May 2014 – MDCA has been operating for 5 years now. In that time, the FLEX experiment has completed 414 unique (non-repetitive) test points. The FLEX-2 experiment is current installed in the MDCA and has completed 180 unique tests and has approximately 220 more tests to accomplish. The FLEX-ICE-GA (Italian Combustion Experiment for Green Air) has also started and finished operations and has accomplished 92 unique tests. MDCA is scheduled to continue operating FLEX-2 through June 2015, and will then be reconfigured to operate FLEX-2J (a JAXA experiment) through December 2015.
A new experiment that has been approved to operate in the CIR is the Cool Flames Investigation (CFI) (CFI’s website). This experiment is a response and focused investigation of a phenomenon discovered while running the FLEX experiments and seen during FLEX-2 and FLEX-ICE-GA tests. CFI will be launched in February of 2016 and will run for up to 6 months, after which the CIR will be reconfigured again with a new gaseous combustion insert and suite of experiments, called Advanced Combustion via Microgravity Experiments (ACME). A future insert that will study solid combustion, the Solid Ignition and Extinction Experiment (SoFIE), is being planned to follow ACME in the CIR. Both the ACME and SoFIE inserts use the design heritage of the MDCA to interface with the CIR.
The modular design of the MDCA has allowed for multiple orbital replacement units (ORUs) to be installed when the initial hardware has either failed, operated ineffectively, been consumed, or has been replaced as part of regular maintenance. To date, crew has replaced the following items:
A spare MDCA color camera will be flown on ATV-5 and may replace the original camera soon.
The Multi-user Droplet Combustion Apparatus (MDCA) is a multi-user facility designed to accommodate different droplet combustion science experiments. The MDCA will conduct experiments using the Combustion Integrated Rack (CIR) of the NASA Glenn Research Center’s Fluids and Combustion Facility (FCF). The payload is planned for the International Space Station. The MDCA, in conjunction with the CIR, will allow for cost effective extended access to the microgravity environment, not possible on previous space flights. It is currently in the Engineering Model build phase with a planned flight launch with CIR in 2008.
As a result of the concurrent design process of MDCA and CIR, the MDCA team continues to work closely with the CIR team, developing Integration Agreements and an Interface Control Document during preliminary integration activities. Integrated testing of hardware and software systems will occur at the Engineering Model and Flight Model phases. Because the engineering model is a high fidelity unit, it will be upgraded to a flight equivalent Ground Integration Unit (GIU) when the engineering model phase is completed. The GIU will be available on the ground for troubleshooting of any on-orbit problems. Integrated verification testing will be conducted with the MDCA flight unit and the CIR flight unit. Upon successful testing, the MDCA will be shipped to the Kennedy Space Center for a post-shipment checkout and final turn-over to CIR for final processing and launch to the International Space Station.
Once on-orbit, the MDCA is managed from the GRC Telescience Support Center (TSC). The MDCA operations team resides at the TSC. Data is transmitted to the PI’s at their home sites by means of TREK workstations, allowing direct interaction between the PI and operations staff to maximum science. Upon completion of a PI’s experiment, the MDCA is reconfigured for the next of the three follow-on experiments or ultimately removed from the CIR, placed into stowage, and returned to Earth.
Experiments Using the MDCA
The FLEX experiment was designed to assess and quantify the effectiveness of inert-gas suppressants in microgravity and obtain the most conservative estimate of the limiting oxygen index for steady combustion. FLEX is studying the behavior of near-limit diffusion flames examining in detail liquid- and gas-phase transport and chemical kinetics, and developed and is validating detailed and reduced-order transport and chemistry models that are the foundation for real engine simulations.
The second in the FLEX series of experiments, the FLEX-2 investigation uses fuels and environmental conditions that mimic real combustor conditions. The investigation will extend and advance the research into droplet combustion, studying the influence of sub-buoyant convective flows on combustion rates, determining the influence of a second burning droplet on a linear array, and beginning the study of practical fuels by burning bi-component and surrogate fuels. As the research extends into increasingly complex fuels, FLEX-2 data can help verify models of real fuels used in transportation and industry. Results of the FLEX-2 experimental data will help to develop verified detailed and reduced-order models of droplet combustion, particularly with flow-field and droplet-droplet interactions.
The FLEX-Italian Combustion Experiment for Green Air will
test surrogate fuels as defined by the Italian Space Agency
(ASI) within the CIR in the FLEX-2 configuration. A
collaborative agreement between U.S. and Italian scientists
from the Italian National Research Council–Istituto Motori
will allow collaboration on research into biologically
derived fuels (bio-fuels) in an investigation into new,
green energy sources. Researchers from the NRC–Istituto
Motori have identified the fuels to be used as 50–50 mixtures
of n-heptane/ethanol and 50–50 n-hexanol/n-decane.
The FLEX-2J experiment is a joint effort between NASA and the Japanese Space Agency, JAXA, as well as Nihon University and Yamaguchi University. Derived from the JAXA Group Combustion Experiment science objectives, the FLEX-2J will complement those goals using the NASA FLEX-2 hardware and combustion facilities on ISS. FLEX-2J will observe and measure fuel droplet motions during flame spreading along a one-dimensional droplet array. Three droplets will be deployed to fixed positions upon ceramic beads on a silicon carbide fiber. Then an additional three to ten movable droplets are positioned to the fiber at known locations. The first fixed droplet is ignited and the flame is propagated down the array from droplet to droplet. The subsequent burning and motions of the unpinned droplets are recorded; particularly the velocities of the free droplets before and after flame spread are measured. In addition, the experiment will obtain the history of flame leading edge position, flame spread limit span, and the growth process of the group flame along the fuel droplet array. Specifically, the experiment will measure burning rate, burning time, flame spread and droplet motion as a function of inter-droplet spacing, ambient pressure and gas composition.
MDCA/CIR Testing and Integration
Integrated testing between the MDCA hardware and CIR carrier will be performed on the engineering units of both pieces of hardware. Both units are hi-fidelity, flight-like units. Testing, planned for December 2002 will include a full array of sub-package testing, leading to a full end-to-end functional test. Upon completion, the MDCA Engineering Model (EM) will undergo vibration & microgravity testing, EMI/EMC, and acoustical testing. In parallel with EM environmental testing, the MDCA flight hardware will be procured and assembled. Testing will be conducted on the flight unit in early summer 2005 in preparation for a turn-over of the hardware to CIR for flight integrated testing in August 2005.
Launch of the MDCA Hardware
The MDCA hardware will be launch as stowed hardware on the same incremental flight launch as the CIR. This hardware will include the MDCA common hardware and experiment unique hardware for the first droplet investigation, Flame Extinguishment Experiment (FLEX). The Chamber Insert Assembly, MDCA Avionics Package, and experiment unique hardware will be separate stowed items. Once on-orbit, the CIA and Avionics Package will be removed from stowage. The avionics package will be installed on the CIR rack and the CIA will be inserted into the CIR combustion chamber. Experiment unique diagnostics for the first experiment will be installed on the CIR optics bench.
Contacts at NASA Glenn Research Center
August 21, 2009 - MDCA has been installed
into the Combustion Integrated Rack (CIR) on the ISS and has completed
its calibration testing. Science
burns were initiated in April 2009 for the FLEX set of experiments. As
of August 2009, a set of approximately 20 burns have been performed. Science
operations were suspended while reinstall of boot parameters were required
for the MDCA Avionics Box. Science operations (burns) will resume